As the jurist William Blackstone (1723–1780) put it in his eponymous rule, “It is better that ten guilty persons escape than that one innocent suffer.” And so juries in criminal trials make a “presumption of innocence,” and may convict only if the defendant is “guilty beyond a reasonable doubt” (a high setting for β, the criterion or response bias). They may not convict based on a mere “preponderance of the evidence,” also known as “fifty percent plus a feather.”
